Wireless communication scheme with communication quality guarantee and copyright protection

ABSTRACT

A wireless base station which controls joining of a plurality of wireless terminals to a wireless network, stores a maximum joining possible terminal number which indicates a maximum number of the wireless terminals of each terminal type that can join the wireless network simultaneously, and which is set in advance for each one of a plurality of terminal types that classify the wireless terminals, and a currently joining terminal number which indicates a number of the wireless terminals of each terminal type that are currently joining the wireless network, for each one of the plurality of the terminal types. Then, the wireless base station judges whether the joining of one wireless terminal of one terminal type which sent a request message to the wireless network is permitted or not, according to the maximum joining possible terminal number for the one terminal type and the currently joining terminal number stored for the one terminal type.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless base station, a networkjoining control method, a wireless terminal and a communication controlmethod in a wireless network. The present invention also relates to atransmitting device, a receiving device and a wireless base station fortransmitting and receiving various types of contents for which thecopyright protection is necessary via a network.

2. Description of the Related Art

In recent years, in conjunction with the advance of the LAN (Local AreaNetwork) technique, the networking in the office environment has beendeveloped mainly in forms of wired connections among PCs (PersonalComputers).

While such wired LANs are spreading, the use of the wireless LAN inwhich a part of the wired LAN is replaced by radio is also in progress.For example, consider the case where a wireless base station isconnected to the wired LAN and a plurality of portable PCs are connectedto this base station by radio. In this case, when a file of a desk-topPC connected to the wired LAN by Ethernet™ is edited from the portablePC, the radio access to the wired LAN is realized.

Also, when portions of the base station and the portable PC areextracted, these portions form a wireless LAN. The advantages of such awireless LAN are that there is no need to lay cables because radio wavesor infrared rays are used as transmission paths, and that a newconstruction or a layout change of the network is easy.

The introduction of such a wireless LAN is becoming popular due to thestandardization of IEEE 802.11. Namely, the standardization and theresearch and development of the wireless LAN have been made mostly inthe 2.4 GHz band and the 5 GHz band, because of the radiocharacteristics such as a transmission distance and a directivity, thecommunication policy for effectively utilizing the radio bandwidth whichis a limited resource, and in view of the manufacturing cost which ispreferably suppressed as low as possible from a viewpoint of the makers.

Then, in IEEE 802.11, the 2.4 GHz band wireless LAN specification wascompleted in 1997, and the 5 GHz band wireless LAN specification wascompleted in 1999. The wireless network protocols in these frequencybands basically accommodate a plurality of terminals by using the timedivision multiplexing.

In the 2.4 GHz band wireless LAN specification, the transmission rate iseither 1 to 2 Mbps or 11 Mbps, and the specification with thetransmission rate over 20 Mbps is currently under the discussion.Recently, products compatible with this 2.4 GHz band specification havebeen released by many companies so that the base station and thewireless PC card are now priced in an affordable range of general users.

Note that, in this 2.4 GHz band, there is a trend to install theBluetooth™ on all kinds of devices in a variety of fields includingthose of portable telephones, home electronics and PCs. This Bluetooth™is also a wireless system, and it is expected to spread worldwide due toits low cost of about $5 for one chip, its wide acceptance byapproximately 2000 companies in a variety of fields, and Itsstandardization activity that has been made in direct connection withthe product developments.

On the other hand, the 5 GHz band wireless LAN specification can realizethe transmission rate of 20 to 30 Mbps. Also, unlike the 2.4 GHz band, 5GHz band is currently almost unused frequency band in which fastertransmission rates can be expected easily, so that it has a highprospect of becoming the next generation wireless LAN specification, orthe specification for communicating video contents such as those of TVprograms and movies. It is already sold at a price of one chip at $35 in2001, and the LSI development race is expected to become more heated upin the future.

Note that, in addition to the specification made by the IEEE in theU.S.A., there is a specification called HiperLAN2 which is made inEurope, and a specification called wireless 1394 which is made in Japan.In these three specifications, what is called physical layer (PHY layer)in the communication protocol is nearly common, but a way of definingMAC layer is different. As such, 5 GHz band is now becoming familiar.

From the circumstances described above, as wireless devices are spread,the range of application of these techniques is expected to cover notjust the office environment but also the general homes as well. Inparticular, the fact that there is no need to lay cables in the home ispossibly even greater attraction than the case of the officeenvironment. Also, from a viewpoint that it is possible to carry outcommunications of the AV (Audio Visual) data, it is rather expected thattheir needs are higher at the homes.

In the frequency bands such as 2.4 GHz band and 5 GHz band that areintended to be used for the wireless communications, there is apossibility of being influenced by the spatial shape or other devices.In particular, in the case of the contents for which the real timecharacteristic is required, there is a possibility of havingdisturbances in the video or speech due to the occurrence of errors orthe difficulty of the reproduction at constant time interval.

The 2.4 GHz band is used by the existing devices such as the microwaveovens and the portable telephones used in the U.S.A. The IEEE 802.11bwireless LAN and the ad hoc network formed by the Bluetooth devices usethis frequency band, so that they have a possibility of being influencedby these existing devices. They also have a possibility of interferingwith each other at a location where these two types of network coexist.

In the 5 GHz band, the standard specifications such as IEEE 802.11awireless LAN, HiperLAN2, and ARIB wireless 1394™ are established and oneof their major objectives is the faster accommodation of applicationsthan the 2.4 GHz band. In Japan, it is limited to the indoor use, but100 MHz band ranging from 5.15 GHz to 5.25 GHz are released to thepublic and four channels of 20 MHz bandwidth each can be used there. InEurope and U.S.A., other available frequency bandwidths exist.

Compared with the wired communications, the wireless communications areeasier to cause bit errors at the communication path in a middle, whichcan degrade the video and speech if nothing is done. For this reason,the wireless communications employ the FEC (Forward Error Correction)technique in which signals are transmitted after attaching informationfor enabling the correction of errors at a receiving side such as theReed-Solomon coding, or a re-transmission technique in which a receivingside is required to return an acknowledgement and signals are repeatedlyre-transmitted when this acknowledgement is not received.

In the wireless communications, it is possible to determine the bit rateby a combination of the modulation scheme and the coding rate. The superfine AV data such as those of HDTV require a high bit rate. In addition,the isochronicity is required in order to communicate and reproduce theAV data in real time. For this reason, there is a need for a mechanismby which the bandwidth can be secured at interval which is as constantas possible.

Conventionally, there is a concept of the resource reservation forreserving as much of the bandwidth of the network as required by theindividual application. One example of the method for reserving thebandwidth is disclosed in Japanese patent application laid open No.2001-223718.

However, in the method in which the bandwidths declared for the purposeof the resource reservation by the individual connections are simplysummed and the remaining resource is detected according to the sum,there are cases where it is difficult to stably provide thecommunication quality including the guarantee of the isochronicitymentioned above, because of the overhead occurring in relation to thetotal number of connections and the influence due to the variation ofthe transmission bit rate of the individual connection. It isparticularly likely to encounter such cases when the resources are usednear an upper limit of the bandwidth resources allowed by the network.

As described, it has been difficult to guarantee the communicationquality required by each wireless terminal when a plurality of wirelessterminals exist.

Also, in recent years, as the price of the wireless device in compliancewith the specification of IEEE 802.11 or the like is lowering, itbecomes possible to construct the wireless communication system easilyand inexpensively.

Also, there is a trend for the communication speed of the wirelesscommunication system to become faster, so that a difference from a wiredcommunication using communication cables is becomes insignificant interms of the speed.

Recently, it is becoming possible to handle large capacity data such asAV contents easily by a computer for home use, so that it is convenientfor the users if it is possible to transmit and receive data such as AVcontents by using the wireless communication system.

However, if the reproduced signals of the AV contents reproductiondevice such as DVD player are transmitted by radio, it would be possiblefor all the AV contents receiving device within a prescribed range toreceive them.

For this reason, it is possible to consider the use of a mechanism inwhich only the AV contents receiving device which succeeded theauthentication can receive the AV contents, so as to protect thecopyright. However, there is a problem in that if the authentication atthe copyright protection layer succeeds at the AV contents receivingdevice once, it is impossible to distinguish whether this AV contentsreceiving device is a formally permitted device or not.

In order to avoid such a problem, there is a proposition of the wirelesscommunication system which realizes the secure copyright protection bypreventing wireless devices other than those which are formallypermitted to make accesses without a permission, in the wirelessenvironment, as disclosed in commonly assigned co-pending U.S. patentapplication Ser. No. 09/934,674.

However, even when the user A sets up the access control for the deviceby setting an ID indicating that the user A is an owner of the device,if this ID becomes known to a user B who owns another device, the user Bwould be able to make access to the wireless device of the user A. Forthis reason, if the malicious contents owner constructs the wirelesscommunication system and discloses the ID of the device to the public,it becomes possible to distribute the contents with the copyrightprotection, without a permission of the author. Consequently, this isnot a fundamental solution for preventing the illegal distribution ofcontents, from a viewpoint of the copyright protection.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a wirelessbase station, a network joining control method, a wireless terminal, anda communication control method capable of guaranteeing the communicationquality required by each wireless terminal of each terminal type.

It is another object of the present invention to provide a transmittingdevice, a receiving device, and a is wireless base station capable oftightening the copyright protection, without adversely affecting theconvenience of the user.

According to one aspect of the present invention there is provided awireless base station which controls joining of a plurality of wirelessterminals to a wireless network, the wireless base station comprising: afirst memory unit configured to store a maximum joining possibleterminal number which indicates a maximum number of the wirelessterminals of each terminal type that can join the wireless networksimultaneously, and which is set in advance for each one of a pluralityof terminal types that classify the wireless terminals; a second memoryunit configured to store a currently joining terminal number whichindicates a number of the wireless terminals of each terminal type thatare currently joining the wireless network, for each one of theplurality of the terminal types; a reception unit configured to receivea request message for requesting joining to the wireless network fromone wireless terminal of one terminal type; a judgement unit configuredto judge whether the joining of the one wireless terminal which sent therequest message to the wireless network is permitted or not, accordingto the maximum joining possible terminal number stored in the firstmemory unit for the one terminal type and the currently joining terminalnumber stored in the second memory unit for the one terminal type, whenthe request message is received; and a transmission unit configured totransmit a response message indicating a judgement result obtained bythe judgement unit, to the one wireless terminal.

According to another aspect of the present invention there is provided anetwork joining control method at a wireless base station which controlsjoining of a plurality of wireless terminals to a wireless network, thenetwork joining control method comprising: storing a maximum joiningpossible terminal number which indicates a maximum number of thewireless terminals of each terminal type that can join the wirelessnetwork simultaneously, and which is set in advance for each one of aplurality of terminal types that classify the wireless terminals, into afirst memory unit; storing a currently joining terminal number whichindicates a number of the wireless terminals of each terminal type thatare currently joining the wireless network, for each one of theplurality of the terminal types, into a second memory unit; receiving arequest message for requesting joining to the wireless network from onewireless terminal of one terminal type; judging whether the joining ofthe one wireless terminal which sent the request message to the wirelessnetwork is permitted or not, according to the maximum joining possibleterminal number stored in the first memory unit for the one terminaltype and the currently joining terminal number stored in the secondmemory unit for the one terminal type, when the request message isreceived; and transmitting a response message indicating a judgementresult obtained by the judgement step, to the one wireless terminal.

According to another aspect of the present invention there is provided acomputer program product for causing a computer to function as awireless base station which controls joining of a plurality of wirelessterminals to a wireless network, the computer program productcomprising; a first computer program code for causing the computer tostore a maximum joining possible terminal number which indicates amaximum number of the wireless terminals of each terminal type that canjoin the wireless network simultaneously, and which is set in advancefor each one of a plurality of terminal types that classify the wirelessterminals, into a first memory unit; a second computer program code forcausing the computer to store a currently joining terminal number whichindicates a number of the wireless terminals of each terminal type thatare currently joining the wireless network, for each one of theplurality of the terminal types, into a second memory unit; a thirdcomputer program code for causing the computer to receive a requestmessage for requesting joining to the wireless network from one wirelessterminal of one terminal type: a fourth computer program code forcausing the computer to judge whether the joining of the one wirelessterminal which sent the request message to the wireless network ispermitted or not, according to the maximum joining possible terminalnumber stored in the first memory unit for the one terminal type and thecurrently joining terminal number stored in the second memory unit forthe one terminal type, when the request message is received; and a fifthcomputer program code for causing the computer to transmit a responsemessage indicating a judgement result obtained by the judgement unit, tothe one wireless terminal.

According to another aspect of the present invention there is provided awireless terminal that requests a wireless base station to permitjoining of the wireless terminal to a wireless network, the wirelessterminal comprising: a transmission unit configured to transmit arequest message to the wireless base station which manages the wirelessnetwork, the request message containing an indication that the joiningto the wireless network is requested, an information indicating aterminal type of the wireless terminal, and all or a part of values ofprescribed parameters including a minimum bit rate which indicates aminimum bandwidth requested by the wireless terminal, a maximumtolerable jitter with respect to a periodic transmission intervalrequested by the wireless terminal, and a maximum transmission distancerequested by the wireless terminal; and a reception unit configured toreceive a response message indicating a permission of the joining, whichis transmitted by the wireless base station in response to the requestmessage, when it is judged that the joining is permitted as a firstjoining condition based on an upper limit number of terminals that canjoin the wireless network simultaneously which is set in advance for theterminal type contained in the request message is satisfied, and asecond joining condition based on the values of the prescribedparameters contained in the request message is satisfied.

According to another aspect of the present invention there is provided acommunication control method at a wireless terminal that requests awireless base station to permit joining of the wireless terminal to awireless network, the communication control method comprising:transmitting a request message to the wireless base station whichmanages the wireless network, the request message containing anindication that the joining to the wireless network is requested, aninformation indicating a terminal type of the wireless terminal, and allor a part of values of prescribed parameters including a minimum bitrate which indicates a minimum bandwidth requested by the wirelessterminal, a maximum tolerable jitter with respect to a periodictransmission interval requested by the wireless terminal, and a maximumtransmission distance requested by the wireless terminal; and receivinga response message indicating a permission of the joining, which istransmitted by the wireless base station in response to the requestmessage, when it is judged that the joining is permitted as a firstjoining condition based on an upper limit number of terminals that canjoin the wireless network simultaneously which is set in advance for theterminal type contained in the request message is satisfied, and asecond joining condition based on the values of the prescribedparameters contained in the request message is satisfied.

According to another aspect of the present invention there is provided acomputer program product for causing a computer to function as awireless terminal that requests a wireless base station to permitjoining of the wireless terminal to a wireless network, the computerprogram product comprising: a first computer program code for causingthe computer to transmit a request message to the wireless base stationwhich manages the wireless network, the request message containing anindication that the joining to the wireless network is requested, aninformation indicating a terminal type of the wireless terminal, and allor a part of values of prescribed parameters including a minimum bitrate which indicates a minimum bandwidth requested by the wirelessterminal, a maximum tolerable jitter with respect to a periodictransmission interval requested by the wireless terminal, and a maximumtransmission distance requested by the wireless terminal; and a secondcomputer program code for causing the computer to receive a responsemessage indicating a permission of the joining, which is transmitted bythe wireless base station in response to the request message, when it isjudged that the joining is permitted as a first joining condition basedon an upper limit number of terminals that can join the wireless networksimultaneously which is set in advance for the terminal type containedin the request message is satisfied, and a second joining conditionbased on the values of the prescribed parameters contained in therequest message is satisfied.

According to another aspect of the present invention there is provided atransmitting device for transmitting contents for which a copyrightprotection is necessary, to one or more receiving devices through anetwork, the transmitting device comprising: a contents supply unitconfigured to store or generate the contents; a communication processingunit configured to select a communication mode in case of carrying outcommunications with receiving devices; a device authentication and keyexchange processing unit configured to determine a receiving devicenumber indicating a number of receiving devices with whichcommunications can be carried out, according to the communication modeselected by the communication processing unit, and carry out deviceauthentication and key exchange with receiving devices in number whichis less than or equal to the receiving device number; an encryptionprocessing unit configured to encrypt the contents by using a keyexchanged by the device authentication and key exchange processing unit;and a network interface unit configured to transmit the contentsencrypted by the encryption processing unit, to the receiving devices innumber which is less than or equal to the receiving device number.

According to another aspect of the present invention there is provided atransmitting device for transmitting contents for which a copyrightprotection is necessary, to one or more receiving devices through awireless base station via a network, the transmitting device comprising:a contents supply unit configured to store or generate the contents; anID recording unit configured to record in advance a network ID of thewireless base station which is to be used in an authenticationprocessing with the wireless base station; a network ID authenticationprocessing unit configured to carry out authentication of the network IDwith the wireless base station by using the network ID recorded in theID recording unit: a device authentication and key exchange processingunit configured to switch a receiving device number indicating a numberof receiving devices with which communications can be carried out,according to an authentication result obtained by the network IDauthentication processing unit, and carry out device authentication andkey exchange with receiving devices in number which is less than orequal to the receiving device number; an encryption processing unitconfigured to encrypt the contents by using a key exchanged by thedevice authentication and key exchange processing unit; and a networkInterface unit configured to transmit the contents encrypted by theencryption processing unit, to the receiving devices in number which isless than or equal to the receiving device number.

According to another aspect of the present invention there is provided atransmitting device for transmitting contents for which a copyrightprotection is necessary, to one or more receiving devices through anetwork, the transmitting device comprising: a contents supply unitconfigured to store or generate the contents; a communication processingunit configured to select a communication mode in case of carrying outcommunications with receiving devices; a device authentication and keyexchange processing unit configured to determine a key to be used aseither a key that permits a finite number of copies or a key thatprohibits copies, according to the communication mode selected by thecommunication processing unit, and carry out device authentication andkey exchange for the copyright protection with receiving devices; anencryption processing unit configured to encrypt the contents by using akey exchanged by the device authentication and key exchange processingunit; and a network interface unit configured to transmit the contentsencrypted by the encryption processing unit, to the receiving devices.

According to another aspect of the present invention there is provided atransmitting device for transmitting contents for which a copyrightprotection is necessary, to one or more receiving devices through awireless base station via a network, the transmitting device comprising:a contents supply unit configured to store or generate the contents; anID recording unit configured to record in advance a network ID of thewireless base station which is to be used in an authenticationprocessing with the wireless base station; a network ID authenticationprocessing unit configured to carry out authentication of the network IDwith the wireless base station by using the network ID recorded in theID recording unit; a device authentication and key exchange processingunit configured to determine a key to be used as either a key thatpermits a finite number of copies or a key that prohibits copies,according to an authentication result obtained by the network IDauthentication processing unit, and carry out device authentication andkey exchange for the copyright protection with receiving devices; anencryption processing unit configured to encrypt the contents by using akey exchanged by the device authentication and key exchange processingunit; and a network interface unit configured to transmit the contentsencrypted by the encryption processing unit, to the receiving devices innumber which is less than or equal to the receiving device number.

According to another aspect of the present invention there is provided areceiving device for receiving contents for which a copyright protectionis necessary, from a transmitting device via a network, the receivingdevice comprising: a communication processing unit configured to selecta communication mode in case of carrying out communications with thetransmitting device; a device authentication and key exchange processingunit configured to exchange a key that permits a finite number of copiesor a key that prohibits copies with the transmitting device, accordingto the communication mode selected by the communication processing unit,and carry out device authentication and key exchange for the copyrightprotection with the transmitting device: a network interface unitconfigured to receive the contents which are encrypted, from thetransmitting device; and a decryption processing unit configured todecrypt the contents received by the network interface unit, by using akey exchanged by the device authentication and key exchange processingunit.

According to another aspect of the present invention there is provided areceiving device for receiving contents for which a copyright protectionis necessary, from a transmitting device through a wireless base stationvia a network, the receiving device comprising: an ID recording unitconfigured to record in advance a network ID of the wireless basestation which is to be used in an authentication processing with thewireless base station; a network ID authentication processing unitconfigured to carry out authentication of the network ID with thewireless base station by using the network ID recorded in the IDrecording unit; a device authentication and key exchange processing unitconfigured to exchange a key that permits a finite number of copies or akey that prohibits copies with the transmitting device, according to anauthentication result obtained by the network ID authenticationprocessing unit, and carry out device authentication and key exchangefor the copyright protection with the transmitting device; a networkinterface unit configured to receive the contents which are encrypted,from the transmitting device; and a decryption processing unitconfigured to decrypt the contents received by the network interfaceunit, by using a key exchanged by the device authentication and keyexchange processing unit.

According to another aspect of the present invention there is provided awireless base station for receiving contents for which a copyrightprotection is necessary, from a transmitting device via a network, andtransmitting received contents to one or more receiving devices, thewireless base station comprising: a first network ID authenticationprocessing unit configured to carry out an authentication of a networkID with the transmitting device; a second network ID authenticationprocessing unit configured to carry out an authentication of a networkID with the receiving devices; and a revocation information registrationunit configured to register at least one of an Identificationinformation of each transmitting device which should be prohibited totransmit the contents and an identification information of eachreceiving device which should be prohibited to receive the contents;wherein the transmitting device and the receiving devices switch anumber of transmitting devices or receiving devices to carry out deviceauthentication and key exchange or an encryption scheme, according toauthentication results obtained by the first network ID authenticationprocessing unit and the second network ID authentication processingunit.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an exemplary configuration of awireless network system according to the first embodiment of the presentinvention.

FIG. 2 is a block diagram showing an exemplary configuration of a basestation according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing an exemplary configuration of awireless terminal according to the first embodiment of the presentinvention.

FIG. 4 is a sequence chart showing an exemplary operation sequence at atime of a network joining request according to the first embodiment ofthe present invention.

FIG. 5 is a flow chart showing an exemplary processing procedure of thecase at a time of receiving a network joining request according to thefirst embodiment of the present invention.

FIG. 6 is a diagram showing one exemplary management table that can beused by a base station according to the first embodiment of the presentinvention.

FIG. 7 is a diagram showing another exemplary management table that canbe used by a base station according to the first embodiment of thepresent invention.

FIG. 8 is a flow chart showing an exemplary processing procedure for anetwork joining judgement according to the first embodiment of thepresent invention.

FIGS. 9A and 9B are diagrams showing exemplary configurations of anetwork joining request frame according to the first embodiment of thepresent invention.

FIG. 10 is a diagram showing an exemplary configuration of a networkjoining request frame in case of using IEEE 802.11 according to thefirst embodiment of the present invention.

FIG. 11 is a diagram showing an exemplary configuration of a networkjoining response frame in case of using IEEE 802.11 according to thefirst embodiment of the present invention.

FIG. 12 is a sequence chart showing one exemplary operation sequence ata time of an AV data communication according to the first embodiment ofthe present invention.

FIG. 13 is a sequence chart showing another exemplary operation sequenceat a time of an AV data communication according to the first embodimentof the present invention.

FIG. 14 is a diagram showing an exemplary case for explaining abandwidth reservation in AV data communications according to the firstembodiment of the present invention.

FIG. 15 is a sequence chart showing an exemplary operation sequence foran AV data communication setting based on AV/C protocol according to thefirst embodiment of the present invention.

FIG. 18 is a schematic diagram showing an exemplary overallconfiguration of a wireless communication system according to the secondembodiment of the present invention.

FIG. 17 is a block diagram showing an exemplary internal configurationof a wireless base station according to the second embodiment of thepresent invention.

FIG. 18 is a block diagram showing an exemplary internal configurationof a source device according to the second embodiment of the presentinvention.

FIG. 19 is a block diagram showing an exemplary internal configurationof a sink device according to the second embodiment of the presentinvention.

FIG. 20 is a sequence chart showing a processing procedure of a wirelesscommunication system according to the second embodiment of the presentinvention.

FIG. 21 is a flow chart showing a processing procedure of a stnk deviceaccording to the second embodiment of the present invention.

FIG. 22 is a flow chart showing a procedure of an error processing at astep S18 in the processing procedure of FIG. 21.

FIG. 23 is a flow chart showing a processing procedure of a sourcedevice according to the second embodiment of the present invention.

FIG. 24 is a flow chart showing a procedure of an error processing at astep S36 in the processing procedure of FIG. 23.

FIG. 25 is a sequence chart showing a processing procedure of a wirelesscommunication system when a wireless base station does not have a DTCPnetwork ID according to the second embodiment of the present invention.

FIG. 26 is a sequence chart showing a processing procedure of a wirelesscommunication system with a measure against roaming according to thesecond embodiment of the present invention.

FIG. 27 is a block diagram showing an exemplary internal configurationof a source device with a revocation function according to the secondembodiment of the present invention.

FIG. 28 is a flow chart showing a processing procedure of a sourcedevice with a revocation function according to the second embodiment ofthe present invention.

FIG. 29 is a schematic diagram showing an exemplary overallconfiguration of a wireless communication system according to the thirdembodiment of the present invention.

FIG. 30 is a schematic diagram showing an exemplary case of setting DTCPnetwork ins of all devices to be identical in the wireless communicationsystem of FIG. 29.

FIG. 31 is a sequence chart showing a processing procedure of a wirelesscommunication system in an ad hoc mode according to the secondembodiment of the present invention.

FIG. 32 is a flow chart showing a processing procedure of a sink deviceaccording to the third embodiment of the present invention.

FIG. 33 is a flow chart showing a processing procedure of a sourcedevice according to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 to FIG. 15, the first embodiment of the presentinvention will be described in detail.

FIG. 1 shows an exemplary configuration of a wireless network systemaccording to the first embodiment, which comprises a wireless basestation (which will be referred hereafter as base station) for managinga wireless network 3, and wireless terminals 2 which join the wirelessnetwork 3 after making a joining request to the base station 1 andreceiving a permission. In the wireless network of FIG. 1, it is assumedthat many wireless terminals can exist besides two wireless terminalsshown in the figure.

Note that the wireless network is not limited to any specific type. Forexample, it can be a network according to any one of Bluetooth™, IEEE802.11, HiperLAN2, ARIB wireless 1394™, etc.

FIG. 2 shows an exemplary configuration of the base station 1 in thisembodiment. As shown in FIG. 2, the base station 1 has a communicationunit 11 for carrying out communications with the wireless terminals 2,and a wireless network management unit 12 for carrying out themanagement of the wireless network such as giving a permission or arefusal according to prescribed judgement criteria when a networkjoining request (network joining request message) is received from thewireless terminal 2.

FIG. 3 shows an exemplary configuration of the wireless terminal 2 inthis embodiment. As shown in FIG. 3, the wireless terminal 2 has acommunication unit 21 for carrying out communications with the basestation 1 or the wireless terminal 2, a joining request unit 22 formaking the network joining request to the base station 1 whenevernecessary such as at a time of the AV data transfer, and an AVprocessing unit 23 for carrying out the processing for transmitting orreceiving the AV data.

The exemplary configuration of FIG. 3 is an example in which thewireless terminal 2 has a function of operating as a transmitting sideand/or a receiving side of the AV data. It is also possible to provideprocessing units for the other prescribed functions, in addition to theAV processing unit 23 or instead of the AV processing unit 23.

Note that, in the following, when the wireless terminal 2 has a functionof operating as a transmitting side and/or a receiving side of the AVdata as an example, such a wireless terminal will also be referred to asan AV data terminal.

FIG. 4 shows an exemplary processing sequence at a time of the joiningrequest in this embodiment.

Usually, in the wireless network protocol, the information regarding thewireless network which is a management target is broadcasted from thebase station 1 (step S101). According to this information, the wirelessterminal 2 can discover the wireless network and make the joiningrequest. Note that the step S101 is not indispensable, and it is alsopossible to use information other than the information broadcasted fromthe base station 1.

When it is desired or necessary to join the above described network, thewireless terminal 2 transmits the network joining request to the basestation 1 (step S102). Note that the values of prescribed parameters maybe described in the network joining request.

When the network joining request from the wireless terminal 2 in thenetwork is received, the base station 1 carries out the joiningjudgement as to whether the joining is to be permitted or rejectedaccording to the prescribed judgement criteria, for this network joiningrequest (step S103). Note that, in the case where the wireless terminal2 describes values of the prescribed parameters in the network joiningrequest, the base station 1 may carry out the joining judgementaccording to these values of the prescribed parameters.

Then, when the permission or the rejection is determined, the basestation 1 returns a network joining response (network joining responsemessage) corresponding to the permission or the rejection to the requestsource wireless terminal 2 (step S104). Note that, in the case of therejection, the reason for the rejection may be described in the networkjoining response.

When the network joining response is received, the wireless terminal 2learns the permission or the rejection (and the reason for it or thelimitation imposed on it) by referring to this content of the networkjoining response. Then, the wireless terminal 2 can make the next actionaccording to whether it is the permission or the rejection. For example,if it is the permission, the desired data transfer through that networkis attempted. Also, for example, if it is the rejection, the networkjoining request is made again after waiting for awhile, or the networkjoining request is made again by changing the values of the parametersin the case of describing the values of the prescribed parameters in thenetwork joining request, or the fact that the network joining request isrejected is presented to the user, Note that there are many possible sfor the method by which the wireless terminal 2 that has been permittedthe network joining to leave that network. For example, in the casewhere the wireless terminal 2 leaves the network after the networkjoining is permitted by the base station 1, it is possible to carry outa network leaving notification to the base station 1. It is alsopossible for the base station 1 to regard the wireless terminal 2 thathas been joining the network as having left the network when nocommunication is carried out by the wireless terminal for a prescribedperiod of time. It is also possible for the base station 1 to force apart or all of the wireless terminals that have been joining the networkto leave the network when a prescribed condition holds, by issuing anetwork leaving command to the wireless terminal 2 that should leave thenetwork. It is also possible to use more than one of these methods incombination.

In the following, the wireless network management according to thisembodiment will be described, with a main focus on the network joining.

In this embodiment, the types of terminals are classified in advance,and the permission or the rejection for the network joining request isdetermined for each terminal type differently.

FIG. 5 shows an exemplary processing procedure for judging thepermission or the rejection when the base station 1 receives the networkjoining request from the wireless terminal 2.

As shown in FIG. 5, the base station 1 refers to the terminal type inrelation to the network joining request from one wireless terminal 2,and if it is the first type (step S1), the joining control for the firsttype terminal is carried out (step S2), if it is the second type (stepS3), the joining control for the second type terminal is carried out(step S4), and if it is the third type (step S5), the joining controlfor the third type terminal is carried out (step S6).

When it is determined to permit the network joining, the base station 1returns a response indicating the permission to the requesting sourcewireless terminal 2. On the other hand, when it is determined to reject,the base station 1 returns a response indicating the rejection.

There are many possible variations for the way of determining the typo.For example, it is possible to classify a terminal for transmitting andreceiving video data as the first type, a terminal for transmitting andreceiving still image data which does not transmit or receive video dataas the second type, and a terminal which does not transmit or receivevideo data and still image data as the third type. It is also possibleto classify a terminal for transmitting and receiving AV data at highspeed as the first type, a terminal for transmitting and receiving AVdata at low speed as the second type, and any other terminal as thethird type. It is also possible to classify terminals according to thebit rate required by the wireless terminal. It is also possible to usethe application type as the terminal type.

It is also possible to set the type by a combination of classificationaccording to the first method and classification according to the secondmethod, it is also possible to use three or more classification methodssimilarly.

The content of the joining control for the first type terminal, thecontent of the joining control for the second type terminal, and thecontent of the joining control for the third type terminal may beidentical or different.

Note that the case shown in FIG. 5 is an exemplary case of setting threeterminal types, but it is also possible to set two terminal types, orfour or more terminal types, similarly.

In one exemplary content of the joining control, the upper limit n forthe number of terminals that can join the network simultaneously (whichwill be referred to as a maximum number of terminals that can join) isdetermined in advance for each type of terminal, and after the number ofterminals currently joining reaches to this maximum number n ofterminals that can join for one type, the new joining is not permittedfor that type. Note that, when there is an upper limit number N that isuniquely determined for the wireless network for some reason, it ispreferable to set the maximum number n of terminals that can join to bea value smaller than the unique upper limit number N. FIG. 6 shows anexemplary management table for managing the number of terminals that arecurrently joining simultaneously for each one of three terminal types.

In this case, the base station 1 determines to permit the networkjoining if a number obtained by adding one to the number of terminalscurrently joining for that type of terminal does not exceed the maximumnumber n of terminals that can join (or the number of terminalscurrently joining for that type of terminal is less than the maximumnumber n of terminal that can join) on an assumption of giving apermission to the terminal that made the network joining request. Thebase station 1 determines to reject the network joining if a numberobtained by adding one to the number of terminals currently joining forthat type of terminal exceeds the maximum number n of terminals that canjoin (or the number of terminals currently joining for that type ofterminal is equal to the maximum number n of terminal that can join) onan assumption of giving a permission to the terminal that made thenetwork joining request.

In another exemplary content of the joining control, the maximum numbern of terminals that can join the network simultaneously is determined inadvance for each type of terminal similarly as in the above example, andwhen this condition is satisfied, whether another condition is satisfiedor not is judged and the network joining is permitted only when theanother condition is also satisfied.

One example of the another condition is that values of parameters suchas the minimum bit rate, the maximum tolerable jitter, and the maximumtransmission distance are all satisfying reference values determined foreach parameter in advance. Here, the minimum bit rate is a minimumbandwidth required by the AV data terminal. There is a need to carry outthe AV data communications at periodic timings, and the maximumtolerable jitter is the maximum tolerable value for the jitter of thesetimings.

The maximum transmission distance is the maximum value of thetransmission distance desired by the AV data terminal. FIG. 7 shows anexemplary management table for managing the reference values of theparameters and the number of terminals that are currently joiningsimultaneously for each one of three terminal types.

In the examples of FIG. B and FIG. 7, the number of terminals that arecurrently joining is also managed in the management table, but it isalso possible to manage the correspondence between the terminal type andthe number of terminals that are currently joining separately from themanagement table of FIG. 6 or FIG. 7.

Note that it is assumed to be possible to Judge each of the parametersdescribed above. For example, the value of each parameter requested bythe wireless terminal 2 may be described in the network joining request.

It is also assumed to be possible to judge the terminal type. Forexample, the information indicating the terminal type may be describedin the network joining request.

FIG. 8 shows an exemplary detailed procedure at a time of judgingwhether the wireless network joining requested from a terminal of onetype should be permitted or rejected by the base station 1

The base station 1 manages the number of terminals that are currentlyjoining for a terminal type of the AV data terminal.

When the network joining request from the AV data terminal 2 is receivedand it is judged that a terminal type related to the network joiningrequest is the AV data terminal (the first type of FIG. 5, for example)(step S1 of FIG. 5, for example), the base station 1 checks whether thenumber of terminals currently joining has been reaching to the maximumnumber n of terminals that can join or not.

Then, if the number of terminals currently joining has been reaching tothe maximum number n of terminals that can join (step S11 NO), thenetwork joining request is rejected.

On the other hand, if the number of terminals currently joining has notbeen reaching to the maximum number of terminals that can join ((stepS11 YES), the processing proceeds to the check of whether the anothercondition is cleared or not, by referring to the reference value of eachparameter for the corresponding terminal type in the management table ofFIG. 7.

Then, for this network joining request, when the minimum bit rate cannotbe realized (step S12 NO), or the maximum tolerable jitter for theperiodic communication timing cannot be satisfied (step S13 NO), or themaximum transmission distance cannot be achieved (step S14 NO), thisnetwork joining request is rejected.

On the other hand, for this network joining request, when the minimumbit rate can be realized (step S12 YES), the maximum tolerable jitterfor the periodic transmission timing can be satisfied (step S13 YES),and the maximum transmission distance can be achieved (step S14 YES),this network joining request is permitted.

Note that, at the step S12, it is Judged that the minimum bit raterelated to this network joining request can be realized when it is lessthan or equal to the corresponding reference value. Also at the stepS13, it is judged that the maximum tolerable jitter related to thisnetwork joining request can be satisfied when it is less than or equalto the corresponding reference value. Also, at the step S14, it isjudged that the maximum transmission distance related to this networkjoining request can be achieved when it is less than or equal to thecorresponding reference value.

When it is determined to reject, the base station 1 returns a networkjoining response message indicating the rejection to the requestingsource AV data terminal 2.

On the other hand, when it is determined to permit the network joiningrequest, the base station 1 returns a network joining response messageindicating the permission to the requesting source AV data terminal 2.In addition, the corresponding number of terminals currently joining forthis terminal type is increased by one.

Note that when any wireless terminal 2 of this terminal type is to behandled as leaving, the corresponding number of terminals currentlyjoining is to be decreased by one.

Now, it is possible to maintain an identifier of the currently joiningwireless terminal for each terminal device. In this case, when thepermission is given to some wireless terminal 2, the base station 1stores its identifier into a device list corresponding to the type ofthe wireless terminal 2, and when the wireless terminal 2 (of thespecific type) for which the identifier is stored in the device list forthe specific type which is actually maintained by the base station 1 isto be handled as leaving, this identifier will be deleted from thedevice list for that type.

Note that FIG. 8 is just an example, and it is not absolutely necessaryto judge the minimum bit rate, the maximum tolerable jitter and themaximum transmission distance in this order. However, basically, it ispreferable to judge them in the order of their importance.

Also, the minimum bit rate, the maximum tolerable jitter and the maximumtransmission rate may be judged in parallel.

Also, FIG. 8 is just an example, and it is possible to use the otheritems for the judgement, in addition to or instead of all or a part ofthe minimum bit rate, the maximum tolerable jitter and the maximumtransmission distance. For example, it is possible to require the AVdata terminal to present the application type used by the AV dataterminal, and permit the joining only to the AV data terminal having theapplication type that is set in advance.

It is also possible to provide a table of all combinations of theJudgement conditions, such that the judgement can be made by referringto this table when the network joining request is received.

By carrying out the management of the AV data terminals and applying alimitation to the network joining in this way, it is possible toguarantee the quality of the AV data communications.

Also, by using the Judgement methods according to the terminal typessimilarly for each type of terminals other than the AV data terminals,it is possible to guarantee the prescribed communication qualityrequired by the terminals of that type.

FIG. 9A shows an exemplary Information contained in the network joiningrequest, in the case where the terminal type, the minimum bit rate, themaximum tolerable jitter, and the maximum transmission distance are tobe described in the network joining request, in the exemplary procedureof FIG. 8.

A “frame type” indicates that it is a radio frame of the network joiningrequest message. According to this frame type, the base station 1recognizes that it is the network joining request message.

A “terminal type” indicates the terminal type described above. Forexample this information indicates that it is the AV data terminaldescribed above.

Also, the “minimum bit rate”, the “maximum tolerable jitter”, and the“maximum transmission distance” described above are also contained.

Note that the information other than those shown in FIG. 9A may be alsocontained in the network joining request message.

For example, as shown in FIG. 5B, an “application type” may becontained. This application type can indicate whether it is an MPEG2application or a DV application, for example.

Also, for example, the FEC (Forward Error Correction) scheme andcapability implemented in the AV data terminal may be contained, and itis possible to judge the permission for the network joining request alsoaccording to whether the information regarding this FEC is available inthe wireless network managed by the base station 1 or not.

FIG. 10 shows an exemplary packet configuration for the network joiningrequest in the case of using the IEEE 802.11 as the wireless networkprotocol.

In the IEEE 802.11, the Association to the base station 1 is requestedby using the Association Request frame as the network joining requestmessage. At this point, the Capability Information field plays animportant role. The information corresponding to the frame type of FIG.9A is described inside the header portion of FIG. 10. As for theinformation corresponding to the terminal type of FIG. 9A, the terminalwhich reserves the bandwidth can be identified by sub-fields such as CFPollable or CF Poll Request or Privacy in the Capability Informationfield. The Information on the maximum tolerable jitter, the maximumtransmission distance, and the application type of FIG. 9B can benotified to the base station by using a Reservation region. ThisReservation region may be used for identifying the terminal in furtherdetail.

FIG. 11 shows an exemplary packet configuration of the network joiningresponse message for the network joining request in the case of usingthe IEEE 802.11 as the wireless network protocol.

In the IEEE 802.11, the Association Response frame is used as thenetwork joining response message to the wireless terminal 2.

In this network joining response message, the judgement result iscontained. Basically, the judgement result is contained in the Statusfield, and the coding shown in FIG. 11 is used to indicate thepermission when the joining is permitted, or the reason for therejection when the joining is rejected.

Note that the coding shown in FIG. 11 corresponds to the exemplaryprocedure of FIG. 8. Also, the reasons for the rejection other thanthose shown in FIG. 11 may be contained in the Status field.

Note that FIG. 11 shows an exemplary coding for the case of indicatingonly one reason for the rejection, but it is also possible to notify thepresence/absence of each reason for the rejection in the ease of therejection, by using the bit map, for example.

Next, an exemplary case of carrying out the AV data transfer between theAV data terminals 2 will be described.

Here, the wireless terminal on a side for transmitting the AV data willbe referred to as an AV data terminal T, and the wireless terminal on aside for receiving the AV data will be referred to as an AV dataterminal R.

FIG. 12 shows an exemplary processing sequence in this case.

Similarly as FIG. 4, the information regarding the management targetwireless network is broadcasted from the base station 1 (step S31).Then, the AV data terminal R makes the network joining request (stepS32).

The base station 1 receives this network joining request and carries outthe joining judgement (step S33). Here, it is assumed that thepermission of the joining is determined. In this case, the base station1 returns the network joining response indicating the permission to theAV data terminal 2 (step S34).

It is also assumed that the network joining request, the joiningjudgement, and the network joining response indicating the permissionare carried out similarly ror the AV data terminal T (steps S35 to S37).

Note that an order of a series of processing of the steps S32 to S34 anda series of processing of the steps S35 to S37 is arbitrary. Also, aseries of processing of the steps S32 to S34 and a series of processingof the steps S35 to S37 may be carried out in parallel.

By the above, the AV data terminal T and the AV data terminal R can jointhe network, and as a result, it is possible to carry out the AV datatransfer between the AV data terminal T and the AV data terminal R.

Next, the AV data terminal T transmits the AV communication request forrequesting the AV data communication with the AV data terminal R, to theAV data terminal R (step S38). This AV communication request containsinformation such as a bit rate, a network occupation time within oneperiod, etc., for example.

When this AV communication request is received, the AV data terminal Rcarries out an admission control for judging the permission or therejection for this request, according to the above described informationcontained in the AV communication request.

Then, when the request is to be permitted, the AV data terminal Rtransmits the AV communication notification indicating that the AV datacommunication will be carried out, to the base station 1, so as toobtain the permission for the periodic use of the network (step S40).The AV data requires the communication at nearly constant interval, andthe limitation for the fluctuation (jitter) of the interval oftenexists.

When this AV communication notification is received, the base station 1carries out an admission control for Judging the permission or therejection of the use of the network, according to the networkutilization state or the like (step S41).

Then, when the use of the network is to be permitted, the base station 1returns the AV returns the AV communication response indicating thisfact to the AV data terminal R (step S42).

When this AV communication response indicating the permission to use thenetwork is received, the AV data terminal R returns the AV communicationresponse to the AV data terminal T (step S43). After receiving this AVcommunication response, the AV data terminal T becomes possible to carryout the AV data communication with the AV data terminal R.

Note that, in the AV communication response, it is possible to describethe Information indicating the fact that the AV data communication ispermitted, and the periodic timing, the bit rate, and the duration oftime by which the network will be occupied. In this case, the AV dataterminals T and R can learn the information indicating the fact that theAV data communication is permitted, and the periodic timing, the bitrate, and the duration of time by which the network will be occupied, byreceiving this AV communication response.

Then, the transfer of the desired AV data is carried out between the AVdata terminal T and the AV data terminal R (step S44).

FIG. 13 shows another exemplary processing sequence in this case. InFIG. 13, the steps S51 to S57 by which the AV data terminals T and Rjoin the wireless network are similar to the steps S31 to S37 of FIG.12, but the procedure for starting the AV data communication isdifferent from FIG. 12. In FIG. 12, the admission control operations arecarried out at two steps of S39 and S41 by the AV data terminal R andthe base station 1, respectively, but in FIG. 13, these admissioncontrol operations are carried out by the base station 1 at the stepS59.

Namely, in this case, the AV data terminal T transmits the AVcommunication request to the base station 1 rather than the AV dataterminal R, so as to request the AV data communication with the AV dataterminal R and to obtain the permission for the periodic use of thenetwork (stop S58). This AV communication request contains informationsuch as a bit rate, a network occupation time within one period, etc.,for example, as described above.

When this AV communication request is received, the base station 1carries out an admission control for judging the permission or therejection for this request, according to the above described informationcontained in the AV communication request and the network utilizationstate or the like (step S59).

Then, when the network use is to be permitted, the base station 1returns the AV communication response and notification indicating thisfact to each one of the AV data terminal T and the AV data terminal R(steps S60, S61).

Then, the transfer of the desired AV data is carried out between the AVdata terminal T and the AV data terminal R (step S62).

Now, with reference to FIG. 14, the bandwidth reservation in the AV datacommunication will be described.

The radio frame is repeated in cycles of a period T. In the IEEE 802.11,such a cycle is formed as the beacon is periodically transmitted fromthe base station 1.

The first AV data communication (indicated as A in FIG. 14) is capableof communicating as the joining is permitted at the cycle C₁ with thelow bit rate and the maximum tolerable jitter Δt. On the other hand, thesecond AV data communication (indicated as B in FIG. 14) is capable ofcommunicating in cycles of a period T as the joining is permitted at thecycle C₂ with the high bit rate.

These AV data communications are managed by the base station 1, and thenetwork joining of the AV data terminal 2 is judged on the base of thismanagement.

As in FIG. 14, it is possible to consider the case where the bit ratesare different among the AV data terminals 2. For this reason, it ispossible to manage the number of terminals using each bit rate, and thisinformation may be used for the judgement of the network joining.

As described with references to FIG. 12 and FIG. 13, before carrying outthe AV data communication, a preparation for the AV data communicationis carried out with the correspondent AV data terminal 2 or the basestation 1. For this preparation, various protocols can be used. In thecase of the IEEE 1394, the AV/C protocol is used, so that its messagescan be mounted on the radio frame and utilized. It is also possible toreserve the bandwidth and the periodic timing similarly by using theprotocol such as RTSP, SIP, H.245, H.323, etc.

FIG. 15 shows an exemplary case of using the AV/C command protocol inthe processing of FIG. 12 or FIG. 13.

The AV data terminal T that wishes to carry out the AV datacommunication transmits an AV/C Request message, which is mounted on theradio frame (step S71). This message corresponds to the AV communicationrequest of the step S38 of FIG. 12 or the step S58 of FIG. 13. Notethat, in the case of using the IEEE 802.11 protocol, an acknowledgementAck is returned in response to this Request message frame (step S72).

At the side that received this message (the AV data terminal R in thecase of FIG. 12, the base station 1 in the case of FIG. 13), theinformation such as bandwidth is set in a register space utilized by theAV/C protocol (step S73). Then, a Response is returned to the AV dataterminal T (step S74). This message corresponds to the AV communicationresponse of the step S43 of FIG. 12 or the step S60 of FIG. 13.

Note that, in the AV/C protocol, the Response should be returned within100 ms basically, but when this is difficult, the INTERIM can bedeclared to postpone the formal issuance of the Response (step S76)Also, In the case of the IEEE 802.11, the acknowledgement Ack isreturned to all, the messages (steps S75, S77).

In this way, the preparation before the AV data communication can bemade.

Note that the above description is directed to the case of always givinga permission without any limitation when the network joining request isto be permitted, but it is also possible to given a permission with alimitation when a prescribed condition holds, for example. In this case,the content of the limitation is described in the network joiningresponse and notified to the wireless terminal 2. There are manypossible variations for the limitation, such as a limitation to limitthe period of time during which the network joining is possible when thenetwork is congested, for example.

As described, according to the first embodiment, it is possible toprovide a wireless base station, a network joining control method, awireless terminal, and a communication control method capable ofguaranteeing the communication quality required by each wirelessterminal of each terminal type.

Also, according to the first embodiment, it is possible to utilize theradio bandwidth effectively, by setting the bandwidth larger than thebandwidth requested by the application to the wireless communicationsection, for ex ample. It is possible to make sure that the transmittedcontents will be received, by making this setting according to theinformation regarding the data storage unit of the receiving side or theinformation regarding the error correction capability.

Referring now to FIG. 16 to FIG. 28, the second embodiment of thepresent invention will be described in detail.

FIG. 16 shows an overall configuration of a wireless communicationsystem according to the second embodiment, that contains a transmittingdevice, a receiving device and a wireless base station. The wirelesscommunication system of FIG. 16 has a wireless device (referredhereafter as a source device) 101 having a contents reproductionfunction such as that of a DVD player and a wireless interface fortransmitting contents, and a wireless device (referred hereafter as asink device) 103 for receiving the contents transmitted from the sourcedevice 101 through a wireless base station 102. These source device 101,wireless base station 102 and sink device 103 are connected to a localarea wireless network A.

As shown in FIG. 16, another local area wireless network B differentfrom the local area wireless network A is also formed, and a wirelessdevice (referred hereafter as a source device) 104 having functionssimilar to the source device 101 and a wireless base station 105 havingfunctions similar to the wireless base station 102 are connected to thislocal area wireless network B.

Here, the case where the sink device 103 moves to an area to which thelocal area wireless network B is accessible. Here, “move” is notnecessarily a physical moving, and the case of changing the network towhich it belongs by changing the configuration is also included in thiscase.

Namely, the sink device 103 is assumed to be located within an area atwhich the network A formed by the wireless base station 102 and thenetwork B formed by the wireless base station 105 are both accessible.It is also assumed that the source device 101, the wireless base station102 and the sink device 103 are owned by one person (referred hereafteras Mr. A), and the source device 104 and the wireless base station 105are owned by another person (referred hereafter as Mr. B).

FIG. 16 assumes the case where each one of the source device 101 and thesink device 103 directly carries out the wireless communication throughthe wireless base station 102, but this embodiment is also applicable tothe case where the source device 103 and the sink device 103 do not havethe wireless communication function and a bridge device (not shown)connected by wires to the source device 101 and the sink device 103carries out the wireless communication through the wireless base station102, or the case where the source device 101 and the sink device 103have the wireless communication function but carry out the wirelesscommunication with the wireless base station 102 through the bridgedevice.

Here, the contents are video data or audio data such as MPEG4 data, forexample, which are assumed to be transmitted after applying thecopyright protection. It is also assumed that the contents transmittedby the source device 101 are owned by Mr. A, so that the contents can becopied or viewed only by the private use of Mr. A. Similarly, it is alsoassumed that the contents transmitted by the source device 104 are ownedby Mr. B, so that the contents can be copied or viewed only by theprivate use of Mr. B, and Mr. A is not allowed to copy or view thecontents owned by Mr. B, regardless of whether Mr. B permits or not.

Here, the local area wireless network is assumed to be the IEEE 802.11.The IEEE 802.11 is a kind of the wireless LAN which is implemented inmany PCs currently, and which is expected to be implemented in variousAV devices in future.

The following description is directed to the configuration for realizingthe case where the sink device 103 owned by the Mr. A is capable ofreceiving the contents only from the source device 101 through thewireless base station 102 owned by Mr. A, the access to the sourcedevice 104 through the wireless base station 105 owned by Mr. B islimited, and at the same time the transmission of the contents by thesource device 104 owned by Mr. B to the sink device 103 owned by Mr. Ais also limited, in the situation shown in FIG. 16.

FIG. 17 shows an exemplary internal configuration of the wireless basestation 102 or 105. As shown in FIG. 17, the wireless base station 102or 105 has a 802.11 interface processing unit 111 for executing the IEEE802.11 physical layer processing, a 802.11 communication processing unit112 for executing the IEEE 802.11 datalink layer processing, and a DTCPnetwork ID recording unit 113 for recording a DTCP network ID.

The DTCP network ID is a value uniquely defined for a device at a timeof manufacturing or selling by a manufacturer or a seller, and the ownercan learn but cannot change this value.

FIG. 18 shows an exemplary internal configuration of the source device101 or 104. As shown in FIG. 18, the source device 101 or 104 has acontents storage unit 121 for storing contents, a packet processing unit122 for reading out the contents from the contents storage unit 121 andconverting them into IEEE 802.11 packets, a DTCP device authenticationand key exchange processing unit 123 for carrying out the copyrightprotection processing, a DTCP encryption and decryption processing unit124 for encrypting or decrypting the transmission data, a 802.11communication processing unit 125 for executing the IEEE 802.11 datalinklayer processing, a 802.11 interface processing unit 126 for executingthe 802.11 physical layer processing, a DTCP network ID input unit 127for changing a value of the DTCP network ID, a DTCP network ID recordingunit 128 for recording the DTCP network ID, and a DTCP network IDauthentication processing unit 129 for carrying out the authenticationof the DTCP network ID.

The initial value of the DTCP network ID is a value determined by themanufacturer or seller. The DTCP network ID recording unit 128 has afunction for limiting the number of the DTCP network IDs that can berecorded to a constant value.

Here, the DTCP (Digital Transmission Contents Protection) is thecopyright protection scheme which is the de facto standard in the IEEE1394, USB, etc., In this scheme, the device authentication and keyexchange are carried out between the transmitting device and thereceiving device, for the contents such as AV data for which thecopyright protection is necessary, there is provided a mechanism fortransferring the AV data after encrypting it.

FIG. 19 shows an exemplary internal configuration of the sink device103. As shown in FIG. 19, the sink device 103 has a contentsreproduction processing unit 131 for carrying out a processing to outputpackets to a display or the like, a packet processing unit 132 forconverting the IEEE 802.11 packets received from the base station intothe contents data, a DTCP device authentication and key exchangeprocessing unit 133 for carrying out the copyright protectionprocessing, a DTCP encryption and decryption processing unit 134 forencrypting or decrypting the transmission data, a 802.11 communicationprocessing unit 135 for executing the IEEE 802.11 datalink layerprocessing, a 802.11 interface processing unit 136 for executing the802.11 physical layer processing, a DTCP network ID input unit 137 forchanging a value of the DTCP network ID, a DTCP network ID recordingunit 138 for recording the DTCP network ID, and a DTCP network IDauthentication processing unit 139 for carrying out the authenticationof the DTCP network ID.

Here, what is important is the DTCP network ID input units 127 and 137.As described above, the DTCP network ID recorded at the wireless basestation 102 cannot be rewritten. On the other hand, the source device101 and the sink device 103 can change the DTCP network ID to arbitraryvalue by using the DPCP network ID input unit. However, each one of theDTCP network ID input units 127 and 137 is provided with a register forrecording the number of changes, and the DTCP network ID cannot bechanged more than a prescribed number of times. By this mechanism, theuser has a limited number of times for changing the network ID.

FIG. 20 shows a processing procedure of the wireless communicationsystem in this embodiment. First, the DTCP network ID authentication iscarried out between the sink device 103 and the wireless base station102 (step S201). When this authentication succeeds, the sink device 103makes the DTCP authentication request to the source device 101 (stepS202).

Upon receiving this request, the DTCP network ID authentication iscarried out between the source device 101 and the wireless base station102 (step S203). Then, the DTCP device authentication and key exchangeare carried out between the source device 101 and the sink device 103(step S204). Then, the source device 101 transmits the contentsencrypted by using the key obtained by the key exchange to the sinkdevice 103 through the wireless base station 102 (step S205).

FIG. 21 shows a processing procedure of the sink device 3. First, theuser registers the same DTCP network ID as the wireless base station 102as the DTCP network ID of the sink device 103 in advance (step S211).

Next, whether a value of a number of changes recording register for theDTCP network ID is less than a prescribed value or not is judged (stepS212), and if it is greater than or equal to the prescribed value, theDTCP network ID cannot be changed so that a prescribed error processingis carried out (step S213).

If the value of the number of changes recording register is less thanthe prescribed value, the value of the DTCP network ID is changed and avalue of the number of changes recording register is increased (stepS214). This series of processing will be referred to as a DTCP networkID registration processing.

Note that if the value of the DTCP network ID of the sink device 103 isthe same as that of the wireless base station 102, the processing of thesteps S211 to S214 is unnecessary.

Next, the contents transmission and reception processing is started.First, before carrying out the DTCP device authentication and keyexchange, a mutual authentication processing to check whether values ofthe DTCP network ID of the wireless base station 102 and the DTCPnetwork ID of the sink device 103 coincide or not is carried out (stepS215). This authentication uses the value of the DTCP network ID as theauthentication key, and the secret key cryptosystem as defined byISO/IEC 9798-2. It is also possible to check whether the DTCP networkIDs coincide or not by mutually transmitting the DTCP network ID byattaching a signature and verifying that signature at a receiving sidedevice.

When it is guaranteed that the packets are surely not altered at thewireless link layer and they are those transmitted from the sink device103 to the wireless base station 102, the authentication processing inconjunction with the encryption is not absolutely necessary and it isalso possible to simply transmit the value of the DTCP network ID to thewireless base station 102. In the following, this procedure iscollectively referred to as the DTCP network ID authentication.

When the DTCP network ID authentication succeeded (step S216 YES), thesource device 101 transmits the DTCP device authentication and keyexchange request to the sink device 103 (step S217), whereas when theDTCP network ID authentication failed, the error processing is carriedout (step S218).

FIG. 22 shows a procedure of the error processing at the step S218 ofFIG. 21. The error processing can use: (1) a method for interrupting theDTCP authentication (step S221), or (2) a method for changing thecopying limitation level (step S222), for example.

In the case of (1), it is possible to use a method for not transmittinganything to the source device or a method for transmitting an errormessage for rejecting the DTCP authentication request. As for the caseof (2), in the DTCP, a plurality of levels called CCI (Copy ControlInformation) are defined in order to define the copying limitation bythe copyright owner with respect to the data to be transmitted. Theselevels include Copy Never and No More Copies which prohibit the copying.Copy One Generation which allows the copying only for the onegeneration, and Copy Free which allows the copying freely. Even when theuser specifies the receiving of the contents at a level of Copy OneGeneration with respect to the sink device, if the DTCP network IDauthentication between the sink device and the wireless base stationfails, the sink device is requested to receive the contents at a tightercopying limitation level of Copy Never or No More Copies.

FIG. 23 shows a processing procedure of the source device 101. As shownin FIG. 23, the same DTCP network ID as that of the wireless basestation 102 is also registered at the source device 101 in advance (stepS231). When the DTCP device authentication and key exchange request isreceived from the sink device 103 (step S232), the source device 101carries out the mutual authentication processing to check whether theDTCP network ID values coincide or not with the wireless base station102 (step s233). This authentication can be carried out by the similarprocedure as the authentication used between the sink device 103 and thewireless base station 102 described above.

Next, whether this authentication succeeded or not is Judged (stepS234), and if it succeeded, the DTCP device authentication and keyexchange processing is carried out with the sink device 103 (step S235),whereas if it failed, the error processing is carried out (step S236).

Note that it is also possible to carry out the data concealment andverification processing using the device authentication and key exchangeand the encryption at the wireless link layer as in the IEEE 802.11i,prior to this DTCP network ID authentication.

FIG. 24 shows a procedure of the error processing at the step S236 ofFIG. 23. The error processing can use: (1) a method for discarding theDTCP authentication request received from the sink device 103 andfinishing the DTCP authentication processing (step S241), (2) a methodfor changing the copying limitation level (step S242), (3) a method forlimiting a number of sink devices to which the contents are to bedistributed (step S243), or (4) a method in which the above described(2) and (3) are combined, for example.

In the case of (1), it is possible to use a method for transmitting anerror message for rejecting the DTCP authentication request to the sinkdevice 103, or a method for not responding at all. In the case or (2),even when the sink device 103 requests the contents at a level of CopyOne Generation to the source device 101, if the DTCP network IDauthentication between the source device 101 and the wireless basestation 102 falls, the contents are transmitted at a tighter copyinglimitation level of Copy Never or No More Copies, for example. As forthe case of (3), the DTCP has a function for temporarily limiting thenumber of the sink devices 103 to which the contents are to bedistributed according to a counter for recording the number of the sinkdevices 103, even if the DTCP device authentication and the key exchangeprocessing succeeded, for example. Even when a plurality of sink devices103 request the contents at a level of Copy One Generation, the contentsare distributed at a level of Copy One generation only with respect to aprescribed number of them, and either the authentication is rejected orthe contents are transmitted at a level of Copy Never or No More Copiesfor the other devices in excess of the prescribed number, so as to limitthe number of the sink devices 103 to the prescribed number.

In this way, even if the wireless communication system is constructed byusing the wireless base station 102 which has no DTCP network ID, it ispossible for the source device 101 to transmit the contents to the sinkdevices 103 after applying some limitation. Namely, it becomes possibleto prevent the unlimited copying of the contents by the source device101 with respect to the sink devices 103.

FIG. 25 shows a processing procedure of the wireless communicationsystem of this embodiment in the case where the wireless base station102 does not have any DTCP network ID, which is a procedure forreceiving the contents with CCI of No More Copies at the sink device 103from the source device 101 by using the wireless base station 102 whichdoes not have any DTCP network ID.

Here, it is assumed that the source device 101 can transmit the contentsonly in the case where the contents are requested with CCI of No MoreCopies from the sink device 103, even if the DTCP network ID does notcoincide with the wireless base station 102.

First, the sink device 103 attempts the DTCP network ID authenticationwith respect to the wireless base station 102 (step S251). Thisauthentication processing fails as the wireless base station 102 doesnot have any DTCP network ID (step S252).

Next, the sink device 103 transmits the DTCP device authentication andkey exchange request with CCI of No More Copies to the source device 101(step S253). When this DTCP device authentication and key exchangerequest from the sink device 103 is received, the source device 101attempts the DTCP network ID authentication with respect to the wirelessbase station 102 (step S254). This DTCP network JD authentication may beomitted. This DTCP network ID authentication fails (step S255), but thesource device 101 carries out the DTCP device authentication and keyexchange processing with respect to the sink device 103 because CCI isNo More Copies (step S258). If this authentication succeeds, the sourcedevice 1 transmits the contents to sink device 103 after encrypting thecontents (step S257).

In the above, an exemplary case where the wireless base station 102 is awireless base station that does not have any DTCP network ID has beendescribed, but it is also possible to limit or prohibit the contentstransmission from the source device 101 to the sink device 103 bycarrying out the similar processing even in the case where the DTCPnetwork IDs of the wireless base station 102 and the sink device 103 aredifferent.

Also, even if the sink device 103 and the source device 101 successfullyfinish the DTCP network ID authentication with the wireless base station102 or with each other and the DTCP device authentication and keyexchange processing is normally carried out, it is possible to carry outthe DTCP network ID authentication during the DTCP device authenticationand key exchange processing or the DTCP encrypted contents transmissionprocessing. This is quite effective against the roaming attack in whichthe wireless base station 102 in communication is switched to anotherbase station.

FIG. 26 shows a processing procedure of the wireless communicationsystem with a measure against the roaming. As shown in FIG. 28, it isassumed that the sink device 103 and the wireless base station XX sharethe same DTCP network ID=XX, and the source device 101 and the wirelessbase station YY shares the same DTCP network ID=YY.

Here, the sink device 103 carries out the DTCP network ID authenticationwith respect to the wireless base station XX first (step S261). Thisauthentication succeeds as the wireless base station XX has the sameDTCP network ID=XX. At this point, suppose that the sink device 103changes the base station from the wireless base station XX to thewireless base station YY. This change is made at the wireless datalinklayer so that the layers above the IEEE 802.11 processing unit in thesource device 101 or the sink device 103 cannot know this change.

Next, the sink device 103 transmits the DTCP authentication request tothe source device 101 (step S262), and the source device 101 carries outthe DTCP network ID authentication with the wireless base station YY(step S263). This authentication succeeds as the wireless base stationYY has the same DTCP network ID=YY. Then, the DTCP device authenticationand key exchange processing is carried out between the sink device 103and the source device 101 (step S264).

Here, what is important is that the wireless base station with which thecontents transmission and reception are to be carried out is differentfrom the wireless base station with which the DTCP network IDauthentication was carried out. For this reason, the DTCP network IDauthentication is also carried out at a time of transmitting andreceiving the contents (step S265). In this way, it is possible to checkthat the currently communicating wireless base station is a device whichhas the same DTCP network ID.

In this embodiment, the source device 101 and the sink device 103 arerealizing through the wireless base station 102 a situation in which“the contents transmission and reception processing operates normallybetween devices existing in the same network” and “the contentstransmission and reception processing does not operate normally or alimitation is imposed on the contents transmission and reception betweendevices existing in different network”.

For example, by assigning the same ID to the source device 101, the sinkdevice 103 and the wireless base station 102 which are own by the sameperson Mr. A, it is possible to transmit the contents from the ownsource device 101 to the sink device 103 through the wireless basestation 102. The device manufacturer or seller assigns a unique ID tothe wireless base station and the general users cannot change this ID,so that the ID of the wireless base station 105 owned by a differentperson Mr. B is different from the ID of the wireless base station 102owned by Mr. A. Consequently, it is possible to realize an environmentin which the sink device or the source device 104 owned by Mr. B is setto have the ID of the wireless base station 105 owned by Mr. B, and thecontents will not be transmitted from the source device of Mr. B to thesink device 103 of Mr. A.

In other words, in general, in the case where the interface is wireless,as long as the sink device 103, the wireless base station 102 and thesource device 101 are located within a range in which radio waves can bephysically received, the sink device 103 can transmit a contents requestcommand to the source device 101 to which a different ID is assigned.Consequently, Mr. N who can learn the ID of the wireless base station ofMr. M who owns the source device 101 and the wireless base station 102would be able to receive the contents of Mr. M stored in the sourcedevice, by setting the ID of the own sink device as the ID of thewireless base station of Mr. M, and it would become possible toconstruct an environment in which Mr. M distributes the contents freelyregardless of the presence or absence of the malicious intention.

For the same reason. Mr. P and Mr. Q who can learn the ID of thewireless base station owned by Mr. O would be able to transmit orreceive the contents by setting the ID of their own source device orsink device to be the ID of the wireless base station of Mr. O,regardless of the intention of Mr. O and without making Mr. O aware ofthe intentions of Mr. P and Mr. Q.

For this reason, in this embodiment, the number of times for changingthe ID of the sink device 103 and the source device 101 is limited, soas to limit the changing of the network to which the sink device 103 andthe source device 101 belong.

Now, in FIG. 16, in the case where the DTCP network ID of the local areawireless network changes as in the case where the sink device 103 movesfrom the local area wireless network A to the local area wirelessnetwork B, it suffices to change the DTCP network ID of the sink device103 and the source device 101 from the ID corresponding to the wirelessbase station 102 to the ID corresponding to the wireless base station105.

Also, regarding the DTCP network ID recorded in the DTCP network IDrecording unit 113 of the wireless base station 102, it is possible toenable the purchase of the wireless base station with the identical DTCPnetwork ID, by reporting the DTCP network ID of the previous wirelessbase station used before the purchase of the new wireless base station,to the device manufacturer or seller.

The above description is directed to the case where the source device101 and the sink device 103 transmits and receives contents through asingle wireless base station 2 which has the same DTCP network ID.However, there can be cases where the same person Mr. A owns two or morewireless base stations. In this case, there are various methods forconnecting the DTCP network formed by the plurality of wireless basestations, the source device 101 and the sink device 103. For example, itis possible to use; (1) a method for purchasing the wireless basestations by specifying the DTCP network ID, or (2) a method forproviding a plurality of registers for recording a plurality of DTCPnetwork IDs.

Also, it is useful for the copyright owner to provide a revocationmechanism in which the DTCP network ID of the source device 101 or thewireless base station 102 can be invalidated when it is revealed that amalicious owner of the source device 101 discloses the DTCP network IDof the source device 101 and the wireless base station 102 to the publicso as to construct an environment in which the contents can bedistributed without a permission of the copyright owner.

FIG. 27 shows an internal configuration of the source device 101 with arevocation function. In the configuration of FIG. 27, an improper devicelist recording unit 130 for storing a list of invalid DTCP network IDsis added to the configuration of FIG. 18. The general users cannotrewrite the content of the improper device list recording unit 130.

FIG. 28 shows a processing procedure of the source device of FIG. 27,which differs from the processing procedure of FIG. 23 in that, beforecarrying out the DTCP network ID authentication processing with thewireless base station 102, whether the network ID of the wireless basestation 102 is recorded in the improper device list recording unit 130or not is Judged (step S237), and if it is recorded, the wireless basestation 102 is judged as an improper device and the error processing iscarried out (step S238).

Note that the improper device list recording unit may be provided insidethe wireless base station. In this case, the wireless base stationchecks the improper device list recording unit before carrying out thenetwork ID authentication, and refuses to carry out the network IDauthentication with a transmitting device that is recorded in theimproper device list recording unit.

As described, according to the first embodiment, the number of times forchanging the DTCP network ID is limited, so that it is possible toprevent the malicious use of the contents for which the copyrightprotection is necessary. Also, when the authentication fails, thecontents transmission is permitted after imposing some limitation,rather than completely prohibiting the contents transmission, so thatthe convenience of the user can be improved while realizing thecopyright protection.

In addition, the DTCP network ID authentication is repeated at aprescribed time interval as a measure against the roaming, so that it ispossible to prevent the malicious use of the contents using the roaming.

Also, by storing a list of the invalid DTCP network IDs, it is possibleto discover the improper device quickly.

Referring now to FIG. 29 to FIG. 33, the third embodiment of the presentinvention will be described in detail.

In the second embodiment described above, the source device 101transmits the contents to the sink device 103 through the wireless basestation 102, in contrast, in this third embodiment, the source device101 transmits the contents directly to the sink device 103, withoutusing the wireless base station.

In the IEEE 802.11, a communication mode called ad hoc mode in whichwireless devices communicate without using the wireless base station isdefined. This embodiment is directed to the case of carrying out thecommunications by utilizing the ad hoc mode, and in the following, thedifference from the second embodiment will be mainly described.

FIG. 29 shows a schematic configuration of the wireless communicationsystem according to the third embodiment of the present invention. Asshown in FIG. 29, the source device 101 and the sink devices 103 a, 103b and 103 c are located within a range in which they can carry outcommunications with each other. It is assumed that the sink devices 103a, 103 b and 103 c are owned by Mr. X. The source device 101 records theDTCP network IDs of the sink devices 103 a, 103 b and 103 c in the DTCPnetwork ID recording unit, in order to carry out the DTCP network IDauthentication with the sink devices 103 a, 103 b and 103 c.

In the second embodiment, the DTCP network ID that cannot be freelychanged by the owner is set in the wireless base station 102 in advance,and the contents transmission and reception through the wireless basestation 102 are carried out by setting a value of the DTCP network ID ofthe source device 101 and the sink device 103 to be identical to that ofthe wireless base station 102, in contrast, in the third embodiment,each one of the wireless base station does not exist, so that the sourcedevice 101 and the sink devices 103 a, 103 b and 103 c sets the DTCPnetwork ID to arbitrary value.

However, the number of the DTCP network IDs that can be recorded by eachone of the source device 101 and the sink devices 103 a, 103 b and 103 cis limited to a prescribed number according to the DTCP network IDrecording unit. Also, the source device 101 and each one of the sinkdevices 103 a, 103 b and 103 c must record the same DTCP network ID, sothat the source device 101 cannot transmit the contents to the sinkdevices in excess of the prescribed number, as long as the DTCP networkID is not changed. For the same reason, the sink devices cannot receivethe contents from the source devices in excess of the prescribed number.

As a method for resolving this problem, there is a method for settingthe DTCP network IDs of all the devices owned by Mr. X to be identical.

However, as shown in FIG. 30, if the DTCP network IDs of all the devicesare set to be identical, the DTCP network ID authentication wouldsucceed among all the devices regardless of the owner of the wirelessdevices, so that it is impossible to prevent the contents distributionby the malicious owner of the sink device.

For this reason, in the case of carrying out the communications in thead hoc mode, the same error processing as used when the DTCP network IDauthentication fails in the infrastructure mode is carried out, so as tocarry out the contents transmission after a limitation is imposed.

Namely, there are various possible methods that can be used by the errorprocessing including: (1) a method for discarding the DTCPauthentication request received from the sink device and finishing theDTCP authentication processing, (2) a method for changing the copyinglimitation level, (3) a method for limiting a number of sink devices towhich the contents are to be distributed, or (4) a method in which theabove described (2) and (3) are combined, for example.

FIG. 31 shows a processing procedure of the wireless communicationsystem in the ad hoc mode.

First, each one of the sink devices 103 a, 103 b and 103 c makes theDTCP authentication request with respect to the source device 101 (stepS271). Upon receiving this request, the source device 101 permitscommunications with a limitation (step S272).

Then, the DTCP device authentication and key exchange processing iscarried out between the source device 101 and each one of the sinkdevices 103 a, 103 b and 103 c (step S273). Then, the contents encryptedby using the exchanged key are transmitted from the source device 101 tothe sink devices 103 a, 103 b and 103 c (step S274).

FIG. 32 shows a processing procedure of each one the sink devices 103 a,103 b and 103 c.

Each one of the sink devices 103 a, 103 b and 103 c checks a mode ofcommunications with the source device 101 (step S281).

In the case where the communication mode is the ad hoc mode, the DTCPnetwork ID authentication is not carried out. Of course, it is alsopossible to carry out the DTCP network ID authentication processing, butthe DTCP authentication request is transmitted to the source device 101regardless of whether the authentication succeeds or falls (step S282).

On the other hand, in the case where the communication mode is theinfrastructure mode, the DTCP network ID authentication processing iscarried out with the wireless base station (step S283).

Next, whether the DTCP network IDs coincide or not is judged (stepS284), and if they do not coincide, the processing of the step S282 iscarried out, whereas if they coincide, the DTCP device authenticationand key exchange processing is carried out with the source device 101(step S285).

FIG. 33 shows a processing procedure of the source device 101.

When the DTCP authentication request is received from the sink device103 a, 103 b or 103 c (step S291), the source device 101 checks thecommunication mode next (step S292).

In the case where the communication mode is the ad hoc mode, If therequest of the sink device 103 a, 103 b or 103 c satisfies thelimitation of the source device 101, the DTCP authentication request isaccepted (step S293). For example, in the case where the source device101 limits the number of sink devices to be connected to one, therequest of the sink device which is connected second or subsequent willbe rejected.

On the other hand, in the case where the source device 101 limits thenumber of sink devices that can be permitted at a level of No MoreCopies to five, if the sink device which is connected second isrequesting the DTCP authentication at a level of No More Copies, thisrequest will be accepted.

On the other hand, in the case where the communication mode is theinfrastructure mode, the DTCP network ID authentication processing iscarried out with the wireless base station (step S294), and whether theDTCP network IDs are identical or not is Judged (step S295). If they arenot identical, the processing of the step S293 is carried out, whereasif they are identical, the DTCP device authentication and key exchangeprocessing is carried out (step S296).

In the third embodiment, the device configuration can be simplifiedcompared with the second embodiment, because the DTCP network IDauthentication processing is not absolutely necessary if the sourcedevice 101 and the sink devices 103 a, 103 b and 103 c are supportingonly the communication mode of the ad hoc mode.

For example, in the case where Mr. X owns a portable type sink device (adisplay device, for example), and Mr. X is not necessarily requestingthe storing of the contents from the source device (a DVD player device,for example) of Mr. Y, and wishing only to view it once for all, it ispossible to construct the wireless communication system without settingby using the ad hoc mode, and transmit the contents from the sourcedevice of Mr. Y to the sink device of Mr. X.

In this way, according to the third embodiment, the contents aretransmitted without permitting the copying in the case of carrying outthe communications in the ad hoc mode, so that it is possible to surelyprevent the illegal copying of the contents even if each sink devicesets the DTCP network ID arbitrarily.

Note that, in the embodiments described above, the exemplary case ofusing the IEEE 802.11 as the wireless LAN has been described, but thepresent invention is equally applicable to various types of the wirelessLAN such as the Bluetooth.

As described according to the second and third embodiments, the numberof receiving devices that carry out the device authentication and keyexchange is switched according to the communication mode so that it ispossible to prevent the malicious use of the contents for which thecopyright protection is necessary.

Also, when the authentication fails, the contents transmission ispermitted after imposing some limitation, rather than completelyprohibiting the contents transmission, so that the convenience of theuser can be improved while realizing the copyright protection.

It is to be noted that the above described embodiments according to thepresent invention may be conveniently implemented using a conventionalgeneral purpose digital computer programmed according to the teachingsof the present specification, as will be apparent to those skilled inthe computer art. Appropriate software coding can readily be prepared byskilled programmers based on the teachings of the present disclosure, aswill be apparent to those skilled in the software art.

In particular, the wireless device of the above described embodimentscan be conveniently implemented in a form of a software package.

Such a software package can be a computer program product which employsa storage medium including stored computer code which is used to programa computer to perform the disclosed function and process of the presentinvention. The storage medium may include, but is not limited to, anytype of conventional floppy disks, optical disks, CD-ROMs,magneto-optical disks, ROMs. RAMs, EPROMs, EEPROMs, magnetic or opticalcards, or any other suitable media for storing electronic instructions.

It is also to be noted that, besides those already mentioned above, manymodifications and variations of the above embodiments may be madewithout departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

1-15. (canceled)
 16. A transmitting device for transmitting contents for which a copyright protection is necessary, to one or more receiving devices through a network, in a plurality of communication modes including a first mode in which wireless devices communicate by using a wireless base station and a second mode in which wireless devices communicate without using the wireless base station in a case of carrying out communications with receiving devices, the transmitting device comprising: a contents supply unit configured to store or generate the contents; a device authentication and key exchange processing unit configured to determine a receiving device number indicating a number of receiving devices with which communications can be carried out, such that the receiving device number used in the first mode is greater than the receiving device number used in the second mode, and to carry out device authentication and key exchange with receiving devices in number which is less than or equal to the receiving device number; an encryption processing unit configured to encrypt the contents by using a key exchanged by the device authentication and key exchange processing unit; and a network interface unit configured to transmit the contents encrypted by the encryption processing unit, to the receiving devices in number which is less than or equal to the receiving device number. 17-24. (canceled)
 25. A transmitting device for transmitting contents for which a copyright protection is necessary, to one or more receiving devices through a network, in a plurality of communication modes including a first mode in which wireless devices communicate by using a wireless base station and a second mode in which wireless devices communicate without using the wireless base station in a case of carrying out communications with receiving devices, the transmitting device comprising: a contents supply unit configured to store or generate the contents; a device authentication and key exchange processing unit configured to determine a key to be used as either a key that permits a finite number of copies or a key that prohibits copies and to receive a device number indicating a number of receiving devices with which communications are to be carried out by using a key that permits a finite number of copies, such that the receiving device number used in the first mode is greater than the receiving device number used in the second mode, and to carry out device authentication and key exchange for the copyright protection with receiving devices; an encryption processing unit configured to encrypt the contents by using a key exchanged by the device authentication and key exchange processing unit; and a network interface unit configured to transmit the contents encrypted by the encryption processing unit, to the receiving devices.
 26. The transmitting device of claim 25, wherein the device authentication and key exchange processing unit limits a number of receiving devices with which communications are to be carried out by using a key that permits a finite number of copies.
 27. The transmitting device of claim 25, wherein the device authentication and key exchange processing unit selects a key that permits a finite number of copies in a case where the authentication by the network ID authentication processing unit succeeds, and selects a key that prohibits copies in a case where the authentication by the network ID authentication processing unit fails. 28-35. (canceled) 